Sub Slab Advice

[John Gayewski]

FWIW, the fact that it only comes up in UPC Chapter 13 on Healthcare Facilities means it's not generally required. Although it still may be a good idea.

Shallow frost protected foundations use a wing of insulation outside the building footprint to raise the frost line under the foundation. I wonder if a strip of buried insulation board on top of the sewer lateral would work similarly. It might need to be impractically wide to be effective, though.

Cheers, Wayne

The detail we followed had both sides of the ditch and top. So you'd have someone hold the sides upright as you backfill the trench. Then cover the top of the trench with foam then cover the foam. The foam ends up breaking up and it's not very good. The heat trace covers that weakness.

This was an engineered design.

 

[John Gayewski]

FWIW, the fact that it only comes up in UPC Chapter 13 on Healthcare Facilities means it's not generally required. Although it still may be a good idea.

Our city and county require the depth. When I've worked in Illinois those cities have required the depth. The code part of it was thre first place I found it. I'm sure it's covered in other sections by other wording. The only reason I have to be sure that it's covered by general code or plumbing code is because it's so basic in my experience.

 

[Sponsor]

 

[Jayjayla]

Wow, 48" in Iowa. I'm 36" in Idaho, climate zone 6. I've always just sized up to 4" once I leave the footing just in case but I don't think that is even needed. There is never standing water and always a lot of heat generation. 24"+ under dirt so no wind chill. Again, I've never seen anyone here question it.

As far as soul on top of leech field. I think it's an air thing. Not enough air to grow enzymes or whatever to break things down. Nonsense really since my soil is rocky and drains quickly. Probably another one size fits all approach that codes get wrong. We'll see, I think some sanitarian use logic and bend the rules

 

[John Gayewski]

Wow, 48" in Iowa. I'm 36" in Idaho, climate zone 6. I've always just sized up to 4" once I leave the footing just in case but I don't think that is even needed. There is never standing water and always a lot of heat generation. 24"+ under dirt so no wind chill. Again, I've never seen anyone here question it.

As far as soul on top of leech field. I think it's an air thing. Not enough air to grow enzymes or whatever to break things down. Nonsense really since my soil is rocky and drains quickly. Probably another one size fits all approach that codes get wrong. We'll see, I think some sanitarian use logic and bend the rules

Our frost line is actually 42". The 48" is just how they are designed to be below that and have the pipe above the footing.

A pipe that is frozen will create an ice dam every time water passes over it, it gets thicker. Since there's no hot water sitting on it there's no reason for it to melt.

I don't actually remember thre last time the frost line actually reached 42".

 

[Jayjayla]

Our frost line is actually 42". The 48" is just how they are designed to be below that and have the pipe above the footing.

A pipe that is frozen will create an ice dam every time water passes over it, it gets thicker. Since there's no hot water sitting on it there's no reason for it to melt.

I don't actually remember thre last time the frost line actually reached 42".

Well you're a plumber, I am not. I just know I've never had any issues whatsoever. Could be because my wife takes crazy long showers!

 

[Jayjayla]

Ok, how's this look? Kinda hard to draw the lav vent but I assume the toilet wye downstream of the lav is what matters. so the lav will just why straight vertical into the wall off the main 3" line. Shower has dry vent.

 

[John Gayewski]

Ok, how's this look? Kinda hard to draw the lav vent but I assume the toilet wye downstream of the lav is what matters. so the lav will just why straight vertical into the wall off the main 3" line. Shower has dry vent.

Looks good to me. If you leave the long run of main in the house your gonna want some cleanout. Might want to think about that.

Another advantage of having two exits is you could possibly never have to enter the house if there a plugged line. Not to mention it reduces the chance of clogs.

 

[Jayjayla]

Looks good to me. If you leave the long run of main in the house your gonna want some cleanout. Might want to think about that.

Another advantage of having two exits is you could possibly never have to enter the house if there a plugged line. Not to mention it reduces the chance of clogs.

Ok thanks. I originally had the clean out popping outside of the right bathroom. Now that its all wet vented though seems like I should just do a cleanup in the lav wall over there. Not sure where else I'd put one over there, any suggestions?

 

[wwhitney]

As far as a right side cleanout, you still have the option to extend the 3" all the way to the lav, and that would let you pop outside if desired. Doesn't change the venting, everything is still wet vented.

On the laundry room, if the washer isn't discharging into the sink, the standpipe and laundry sink will need separate vent takeoffs, which can combine in the wall 6" above both flood rims.

On the lower left bath, it's not really shown, but I assume you are having the lav drain join the WC to wet vent it, before the combined drain drops down to join the building drain?

Cheers, Wayne

 

[Jayjayla]

Does this show it more accurately Wayne?

I don't think I'm too worried about a clean out. I'll put one in the lav and kitchen vents since that's probably the most likely to get clogged anyway and you'll be able to snake the 3" from downstream. Also toilets are so easy to remove nowadays in the rare event that I had to snake from the right bath.

 

[Jayjayla]

Ok guys, you probably lost interest in this thread but figured I'd ask anyway. Getting my materials list ready for tomorrow and came across maybe a snag. On the lower left shower since it has to vent on its own, can I come off the main 3" line with a combo wye facing vertical then off the shower trap arm use a 2" combo wye that ties into the 3" but also goes vertical for a vent? It would still be a wet vent I suppose but not tied to the toilet and vanity. Thanks

 

[wwhitney]

The most obvious way to do the lower left shower would be 2" trap arm to a 2" san-tee (just like a sink trap arm), 2" dry vent is on top, the bottom hits an upright 3x2 combo, assuming enough height. [I think you description might have been the same as that, but with a 2" combo instead of a 2" san-tee. Vent takeoffs never use a combo with the trap arm coming into the side entry, that situation requires a san-tee.]

If that doesn't work for some reason, explain, there are plenty of options.

Cheers, Wayne

 

[Jayjayla]

The most obvious way to do the lower left shower would be 2" trap arm to a 2" san-tee (just like a sink trap arm), 2" dry vent is on top, the bottom hits an upright 3x2 combo, assuming enough height. [I think you description might have been the same as that, but with a 2" combo instead of a 2" san-tee. Vent takeoffs never use a combo with the trap arm coming into the side entry, that situation requires a san-tee.]

If that doesn't work for some reason, explain, there are plenty of options.

Cheers, Wayne

Thanks Wayne. Yes, that makes sense about the san-tee now that you say it. I guess I was thinking horizontal to horizontal. I suppose with a combo rather than a san-tee it wouldn't be able to vent. I knew it didn't feel right, thanks for clarifying.

 

[Jayjayla]

As far as a right side cleanout, you still have the option to extend the 3" all the way to the lav, and that would let you pop outside if desired. Doesn't change the venting, everything is still wet vented.

On the laundry room, if the washer isn't discharging into the sink, the standpipe and laundry sink will need separate vent takeoffs, which can combine in the wall 6" above both flood rims.

On the lower left bath, it's not really shown, but I assume you are having the lav drain join the WC to wet vent it, before the combined drain drops down to join the building drain?

Cheers, Wayne

One more question Wayne. You mention the washer discharging into the sink, I assume you mean the sink drain line not the sink itself. The easiest path I think would be a 3x2 combo off the main, 2" runs directly under the wall, combo up to washer, continue to laundry sink LS90 up. Combine vents in wall/ceiling and out roof. No problems? Thanks

 

[wwhitney]

One more question Wayne. You mention the washer discharging into the sink, I assume you mean the sink drain line not the sink itself.

No, I meant the sink itself. I.e. if you have a washer standpipe, rather than discharging the washer into the sink basin.

The easiest path I think would be a 3x2 combo off the main, 2" runs directly under the wall, combo up to washer, continue to laundry sink LS90 up. Combine vents in wall/ceiling and out roof. No problems? Thanks

That works fine, 2 separate 2" drain stub-ups for the washer standpipe and the laundry sink. If you wanted to do it with just one stub up, you could, it would just make the in wall DWV more complicated, and you'd want to plan out carefully where to put the stub up.

It's probably obvious, but the stub up for a laundry standpipe should not be under the standpipe. Rather it should be maybe 1' off, to allow for the width of the trap U-bend, a short trap arm, and a san-tee. If you planned carefully you could fit all of that within one stud bay and stub-up accordingly.

Cheers, Wayne

 

[Jayjayla]

No, I meant the sink itself. I.e. if you have a washer standpipe, rather than discharging the washer into the sink basin.


That works fine, 2 separate 2" drain stub-ups for the washer standpipe and the laundry sink. If you wanted to do it with just one stub up, you could, it would just make the in wall DWV more complicated, and you'd want to plan out carefully where to put the stub up.

It's probably obvious, but the stub up for a laundry standpipe should not be under the standpipe. Rather it should be maybe 1' off, to allow for the width of the trap U-bend, a short trap arm, and a san-tee. If you planned carefully you could fit all of that within one stud bay and stub-up accordingly.

Cheers, Wayne

Nothing is obvious to me anymore Wayne. Planning an entire build, all trades from start to finish before breaking ground is turning my brain to mush. The times we live in though. Thanks for the reminder on the offset placement, I would have forgotten.

 

[Jayjayla]

No, I meant the sink itself. I.e. if you have a washer standpipe, rather than discharging the washer into the sink basin.


That works fine, 2 separate 2" drain stub-ups for the washer standpipe and the laundry sink. If you wanted to do it with just one stub up, you could, it would just make the in wall DWV more complicated, and you'd want to plan out carefully where to put the stub up.

It's probably obvious, but the stub up for a laundry standpipe should not be under the standpipe. Rather it should be maybe 1' off, to allow for the width of the trap U-bend, a short trap arm, and a san-tee. If you planned carefully you could fit all of that within one stud bay and stub-up accordingly.

Cheers, Wayne

Hey Wayne....If you have the patience or any desire to take another look at this, please do. My wife made some layout changes in the 11th hour so it gets a little tight around the laundry and second BR bath now. I think its a better layout though so worth the change.

- I plan on the laundry machine and sink to be under the wall, just thought it would be easier to see pushed out a little.
- I'm not sure how to connect the shower and vanity to be able to wet vent the toilet. Do the shower and vanity have to combine before they hit the main 3" (red) line? If so, its sort of a strange angle I think.
- Does the bathroom have to be completely separate? For example, could I drain the laundry sink and vanity together since they're back to back and still have it vent the bathroom under code? Would be much simpler that way.

Thanks again for all your help.

 

[wwhitney]

A horizontal wet vent (a drain for one fixture serving as a vent for another) may only carry bathroom fixtures. So when a lav wet vents a WC only, the individual lav must join the individual WC; downstream of that junction is unregulated by the venting rules. Etc.

How about you post an unmarked floor plan of the half-bath / laundry / 3/4 bath? Then I'll try marking it up.

Cheers, Wayne

 

[Jayjayla]

A horizontal wet vent (a drain for one fixture serving as a vent for another) may only carry bathroom fixtures. So when a lav wet vents a WC only, the individual lav must join the individual WC; downstream of that junction is unregulated by the venting rules. Etc.

How about you post an unmarked floor plan of the half-bath / laundry / 3/4 bath? Then I'll try marking it up.

Cheers, Wayne

Thanks Wayne. You're a heck of a guy.

 

[wwhitney]

Those don't match DWV.v3.pdf.

Wayne